In the field of microfabrication represented by the manufacture of integrated circuit devices, lithographic technology enabling microfabrication with a line width of about 200 nm or less using short wavelength radiations such as an ArF excimer laser (wavelength: 193 nm), F2 excimer laser (wavelength: 157 nm), and the like has been demanded in order to increase the degree of integration in recent years.
As a resist material applicable to such short wavelength radiations, a number of chemical amplification-type radiation-sensitive resin compositions utilizing a chemical amplification effect between a resin component having an acid-dissociable functional group and a photoacid generator which generates an acid upon irradiation with radiations has been proposed. In recent years, radiation-sensitive resin compositions using a copolymer having two or more types of (meth)acrylic recurring units with different lactone structures as a resin component have been proposed (for example, refer to Patent Documents 1 and 2).    Patent Document 1 JP-A-2003-5375    Patent Document 2 JP-A-2003-252933
However, when a still higher degree of integrity is demanded in the field of an integrated circuit element, radiation-sensitive resin compositions are severely required to exhibit various properties, not to mention of basic properties as a resist such as sensitivity and resolution. In particular, strong demands in recent years include a wide common depth of focus (common DOF) to a line-and-space pattern, an isolated line pattern, and/or an isolated space pattern, a minimal line width change due to fluctuation of the bake temperature, and the like.
However, these performances are intricately related to a radiation-sensitive resin composition as well as to a photoacid generator component, additives, and the like. Furthermore, the relation between a chemical structure and characteristics as a resist of the resin component is complicated. Even if a specific resin component is selected, it is extremely difficult to anticipate properties as a resist or to develop a resist that can satisfy the required performance.